CVE-2026-55204 | HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a … | CVSS 7.5 HIGH

Description

HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpack_dht_insert() within src/hpack-tbl.c that fails to validate the return value of hpack_dht_defrag() when the memory pool is exhausted. An attacker can trigger HPACK dynamic table insertions under memory pressure to dereference a NULL pointer and crash HAProxy worker processes, causing denial of service.

Metadata

CVE ID: CVE-2026-55204
State: PUBLISHED
Assigner: VulnCheck
Reserved: 2026-06-16 15:53 UTC
Published: 2026-06-18 16:05 UTC
Last updated: 2026-06-18 17:26 UTC
Primary CWE: CWE-476
NULL Pointer Dereference
Vendor / Product: haproxy / haproxy
Sources: cve.org · NVD

Severity & Metrics

7.5 HIGH CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC — CISA Coordinator

Exploitation: none
Automatable: yes
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
haproxy	haproxy	—	0 ≤ 3.4.0, 9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513

Weakness (CWE)

CWE	Source	Description
CWE-476	cna	NULL Pointer Dereference

CVSS scores (2)

Score	Severity	Version	Source	Vector
8.7	HIGH	4.0	cna	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5	HIGH	3.1	cna	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References (2)